Nope. The PATENTS file specifically says that if Facebook initiates patent litigation (related or unrelated to React) you can counter sue Facebook AND keep your React patent grant.

"...if Facebook or any of its subsidiaries or corporate affiliates files a lawsuit alleging patent infringement against you in the first instance, and you respond by filing a patent infringement counterclaim in that lawsuit against that party that is unrelated to the Software, the license granted hereunder will not terminate under section (i) of this paragraph due to such counterclaim."